Memory device and reading method thereof

A memory device, comprising:

• a memory block, comprising a plurality of memory sub-blocks, wherein the memory block receives a plurality of word line signals through a plurality of word lines respectively, each of the word line signals is commonly received by the memory sub-blocks, and the memory sub-blocks respectively receives a plurality of memory string selection signals;
• and
• a controller, coupled to the memory block, wherein the controller is configured to:
• during a setup period, set the word line signals to a set voltage value;
• during a plurality of reading periods, set a selected word line signal of the word line signals to a selected voltage value, and set at least one deselected word line signal of the word line signals to a deselected voltage value;
• and
• during each of the reading periods, select at least one of the memory sub-blocks to perform a reading operation,
• wherein the reading periods are a plurality of consecutive time periods after the setup period.